1. Field of the Invention
The present invention relates generally to semiconductor devices. More particularly, the present invention relates to a high-permittivity, low-leakage capacitor dielectric comprising silicon-doped zirconium oxide, and a capacitor having such capacitor dielectric.
2. Description of the Prior Art
As semiconductor devices such as dynamic random access memory (DRAM) devices have been highly integrated, sizes of unit cells have been greatly reduced and an operation voltage level has been lowered. One approach to increasing the capacitance is to increase the dielectric constant of the capacitor dielectric. To provide sufficient charge to be stored on smaller and smaller cell areas, high permittivity metal oxides have been studied and some are used as the capacitor dielectric. Examples of such high-permittivity metal oxides include HfO2 and ZrO2. HfO2 has higher dielectric constant compared to SiO2 and Al2O3, however, it exhibits higher leakage current. To reduce the leakage current, the capacitor dielectric film has to be formed thicker, which in turn reduces the capacitance of the capacitor structure.
The typical ZrO2 (pure) or ZrO2-Al2O3 system has reduced leakage current compared to HfO2, presumably due to that Al2O3 in the ZrO2-Al2O3 or ZrO2-Al2O3-ZrO2 dielectric stack can disrupt crystalline grain boundaries of the crystalline ZrO2, and Al2O3 or ZrAlOx can maintain amorphous phase. However, the discrete Al2O3 layer on the other hand causes a large reduction in the effective permittivity (or total capacitance of the dielectric stack), thereby limiting the amount of charge storage and preventing further miniaturization. It is also difficult to scale the ZrO2 component thinner to achieve higher capacitance because it becomes increasingly difficult to crystallize thinner ZrO2 layers towards high permittivity performance without strong leakage degradation due to excess thermal treatments.
Further, in the field of DRAM technology, it has been found that pure ZrO2 often “buckle off” TiN double-sided containers, resulting in dielectric damage and leakage flier behavior. Accordingly, there is a need in this industry to provide an improved capacitor dielectric without the above-described shortcomings.